III-V semiconductors, such as GaAs, InAs, AlAs, InP, or alloys thereof, are materials of interest for metal-oxide semiconductor (MOS) applications as potential replacement of silicon (Si). However, III-V surfaces are prone to oxidization when exposed to air. The native oxides which form on the surface due to this oxidation are of poor quality, e.g. lead to a high density of interface defects and are poor insulators. Such interface defects are known in the art to be detrimental to the performance of semiconductor devices manufactured in or on the III-V semiconductor material.
There is therefore a need in the art for new methods for obtaining III-V semiconductor components having a low density of interface defects between the III-V substrate and an overlaying layer.
Passivation with (NH4)2S solutions has been used for this purpose by E. O'Connor et al. (Appl. Phys. Lett. 99, 212901 (2011)). In this paper, a (NH4)2S passivation layer was formed on the surface of a InGaAs substrate after a cleaning step. This may remove the native oxide, and improve the air stability of the III-V surface, thereby reducing re-oxidation after the cleaning step while the sample is exposed to air, prior to gate oxide deposition or another layer deposition step.
However, such a method does not allow for the passivated III-V substrate to be maintained for an extended time period in air. The transfer to the ALD reactor needed to be performed within 3 minutes. Also, there remains a need for more stable passivation solutions, e.g. providing more stable surfaces in air, and more thorough passivation.